Yes, you can replace the fan heating element, and it's not too difficult a job generally. But do make sure that the electricity is turned off first! If it's a built-in oven you may need the services of a weight lifter to get the thing out of its housing, although in most cases (I think) the job can be done without removing the oven.
Thanks Eric,
I've just had a chat to a very nice local cooker spares supplier who told me the screws should be self tapping,which means it can just be un screwed and removed.
There is a slight possibilty it is held in with nuts and bolts,which means the oven will have to be slid out of the housing to access the nuts.
We had this replace 4 years ago and Sue seems certain that the repair man did not take out the oven from the housing,so
Also the part I priced online with Currys Partmaster was £65.99,my local shop has quoted £29.95